A femtocell is a tiny mobile communication base station for use in the home or home office. That is, the femtocell implies a tiny base station having low output, and provides a wired/wireless convergence service to a user by connecting a mobile phone and the Internet. Typically, the service area of a femtocell is about a 20 m radius. The femtocell improves call performance of an indoor area that cannot be covered by a macrocell or shares a macrocell load in an overload area, and has a merit of communication cost reduction for a user's point of view.
The femtocell uses a specialized technique such as automatic cell-configuration, and solves not only IP address composition and security composition but also interference between a macrocell and a femtocell by using automatic network planning function. In this case, for automatic cell composition, the femtocell should be able to initially or periodically operate in a sniffer mode. In the sniffer mode, the femtocell performs like a terminal that can search neighbor macrocells and femto-cells so that it can generate a neighbor cell list, set power saving control and frequency, and share such information with a neighbor macrocell.
In a conventional cellular system where only macrocells exist, a macrocell includes scanning information such as a neighbor cell list (e.g., a cell ID, a frequency index, a preamble index, and so on) in a mobile neighbor advertisement (MOB_NBR_ADV) message and broadcasts the message to the terminal. Therefore, the terminal can search neighbor macrocells without scanning all macrocells. That is, an unnecessary scanning load can be reduced by eliminating a frequency and a preamble that are not included in the neighbor cell list.
However, if such a method is applied to an environment where a macrocell and a femtocell are overlapped, the macrocell includes not only information on a neighbor macrocell but also scanning information (e.g., a cell ID, a frequency index, a preamble index, and so on) of an overlapped neighbor femtocell in a mobile neighbor advertisement message and broadcasts the message to the terminal in order to support the terminal to search not only neighbor macrocells but also neighbor femtocells.
Since femtocell coverage is very small, many femtocells may exist in one macrocell. Therefore, when all of the neighbor macrocell lists and neighbor femtocell lists are broadcasted to the terminal by using the conventional method, the amount of information related thereto may be rapidly increased. In addition, although the terminal receives all the neighbor macrocell lists and neighbor femtocell lists from the macrocell, scanning delay and power consumption are increased as the terminal scans all neighbor macrocells and neighbor femtocells in the lists. Particularly, when the femtocell uses a frequency that is different from that of the macrocell in consideration of interference therebetween, the cell search load of the terminal is further increased.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.